INTRODUCTION. 11 



Pali. — The palP are the small processes which exist between certain septa and the 

 columella. They generally arise from the base of the visceral cavity, or close to it, 

 and pass upwards, united by one edge to the columella, and by the other to the 

 inner end or margin of the septa. When there is no columella they are adherent to 

 the septa, present a free edge to the cavity in the axis of the corallum, and arise with the 

 septa. 



The upper or free margin of the pali is usually lobed, and is thicker than the end of 

 the septum to which it corresponds ; it may project higher than the end of the septum, and 

 may form a very marked feature in the calicular fossa. 



The sides are more or less broad, and are usually ornamented differently to the septa. 



The inner and outer edges are united to the septa and columella, either by processes 

 or by a perfect fusion. 



The number and size of the pali vary in different species. The pali may exist before 

 (or rather internally to) one or several orders of septa, and they are then said to form one 

 or more crowns. 



The development of the pali has often, but not invariably, a very singular relation to 

 that of certain septa. Thus, when there is but one row or crown of pali ^ they are placed 

 at the inner edge of the penultimate septa ; and when there are two rows, or crowns, they 

 may be seen at the inner edge of the penultimate and antepenultimate cycles of septa. In 

 some corals with numerous septa pali are found in contact with all the septa, except those 

 which have been developed the last — the last cycle. In others the pali are found in 

 relation to all the cycles. One genus has the pali attached to all the septa except those 

 of the cycle which precedes the last, and a genus well marked in the West Indian fossil 

 coral-fauna has no pali before the principal septa, but they exist before the penultimate 

 and antepenultimate cycles. 



There is a curious relation between the perfection of the septal development and the 

 presence of pali. Milne-Edwards and J. Haime have proved that, if in one half of a 

 system the cycles of septa are not complete, there is a corresponding absence of pali ; thus, 

 a coral with four cycles may have pali before the secondary and tertiary septa ; but if one 

 or both of the orders of the fourth cycle are wanting in one half of a system there would 

 be no palulus before the tertiary septum of that half-system. 



When there is a columella the appearance of the pali is generally very distinct, at the 

 same time they may be confounded with its papillae ; but when the calice has been worn 

 away, the attachment of the pali to the columella is often so distinct that they may be mis- 

 taken for the ends of large septa. 



The large spines on the inner end of some septa, or some enlargement of the laminee 

 at that spot, may be mistaken for pali, and the terms paliform tooth and swelling are very 



1 Plate I, figs. 8, 9, 10, 14, 18. 



2 For an exception, see pali in Porites panicea, Lons. 



